When complete control over a system and its reliability is essential, custom applications can offer a benefit to your business. When software is custom built, it gives you control over what features are included, how they are tested, and when they are released.
Certainly, this software does not belong to every situation – if a well-designed, widely used platform offers exactly what you need as a core offering, custom-building it might not make sense. If there is a situation where you need to control specifically when updates occur and how the software is implemented, then it might make sense. By going the custom application route, you will never have to worry about being forced to update in order to take advantage of bug or security fixes, or the risk of having a feature that you depend upon removed from the supported software.